/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.coders;



import com.bff.gaia.unified.sdk.util.common.ElementByteSizeObserver;

import com.bff.gaia.unified.sdk.values.KV;

import com.bff.gaia.unified.sdk.values.TypeDescriptor;

import com.bff.gaia.unified.sdk.values.TypeParameter;



import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.util.Arrays;

import java.util.List;



/**

 * A {@code KvCoder} encodes {@link KV}s.

 *

 * @param <K> the type of the keys of the KVs being transcoded

 * @param <V> the type of the values of the KVs being transcoded

 */

public class KvCoder<K, V> extends StructuredCoder<KV<K, V>> {

  public static <K, V> KvCoder<K, V> of(Coder<K> keyCoder, Coder<V> valueCoder) {

    return new KvCoder<>(keyCoder, valueCoder);

  }



  public Coder<K> getKeyCoder() {

    return keyCoder;

  }



  public Coder<V> getValueCoder() {

    return valueCoder;

  }



  /////////////////////////////////////////////////////////////////////////////



  private final Coder<K> keyCoder;

  private final Coder<V> valueCoder;



  private KvCoder(Coder<K> keyCoder, Coder<V> valueCoder) {

    this.keyCoder = keyCoder;

    this.valueCoder = valueCoder;

  }



  @Override

  public void encode(KV<K, V> kv, OutputStream outStream) throws IOException, CoderException {

    encode(kv, outStream, Context.NESTED);

  }



  @Override

  public void encode(KV<K, V> kv, OutputStream outStream, Context context)

      throws IOException, CoderException {

    if (kv == null) {

      throw new CoderException("cannot encode a null KV");

    }

    keyCoder.encode(kv.getKey(), outStream);

    valueCoder.encode(kv.getValue(), outStream, context);

  }



  @Override

  public KV<K, V> decode(InputStream inStream) throws IOException, CoderException {

    return decode(inStream, Context.NESTED);

  }



  @Override

  public KV<K, V> decode(InputStream inStream, Context context) throws IOException, CoderException {

    K key = keyCoder.decode(inStream);

    V value = valueCoder.decode(inStream, context);

    return KV.of(key, value);

  }



  @Override

  public List<? extends Coder<?>> getCoderArguments() {

    return Arrays.asList(keyCoder, valueCoder);

  }



  @Override

  public void verifyDeterministic() throws NonDeterministicException {

    verifyDeterministic(this, "Key coder must be deterministic", getKeyCoder());

    verifyDeterministic(this, "Value coder must be deterministic", getValueCoder());

  }



  @Override

  public boolean consistentWithEquals() {

    return keyCoder.consistentWithEquals() && valueCoder.consistentWithEquals();

  }



  @Override

  public Object structuralValue(KV<K, V> kv) {

    if (consistentWithEquals()) {

      return kv;

    } else {

      return KV.of(

          getKeyCoder().structuralValue(kv.getKey()),

          getValueCoder().structuralValue(kv.getValue()));

    }

  }



  /** Returns whether both keyCoder and valueCoder are considered not expensive. */

  @Override

  public boolean isRegisterByteSizeObserverCheap(KV<K, V> kv) {

    return keyCoder.isRegisterByteSizeObserverCheap(kv.getKey())

        && valueCoder.isRegisterByteSizeObserverCheap(kv.getValue());

  }



  /** Notifies ElementByteSizeObserver about the byte size of the encoded value using this coder. */

  @Override

  public void registerByteSizeObserver(KV<K, V> kv, ElementByteSizeObserver observer)

      throws Exception {

    if (kv == null) {

      throw new CoderException("cannot encode a null KV");

    }

    keyCoder.registerByteSizeObserver(kv.getKey(), observer);

    valueCoder.registerByteSizeObserver(kv.getValue(), observer);

  }



  @Override

  public TypeDescriptor<KV<K, V>> getEncodedTypeDescriptor() {

    return new TypeDescriptor<KV<K, V>>() {}.where(

            new TypeParameter<K>() {}, keyCoder.getEncodedTypeDescriptor())

        .where(new TypeParameter<V>() {}, valueCoder.getEncodedTypeDescriptor());

  }

}